The primary objective of this prospective, multidisciplinary study is to identify risk factors which predispose individuals to develop asthma and other manifestations of allergic disease on exposure to laboratory animals in the workplace. This proposal is to continue a study which was originally funded for 3 years. Specific objectives relate to two major questions under investigation. First, what are the factors which increase the risk of allergic asthma, as measured by relative risk? Factors of potential importance include: airway hyperreactivity; personal or family history of allergy or asthma; skin test sensitivity to animal or other aeroallergens; IgE and IgG antibody levels to animal allergens; demographic and psychosocial factors; and workplace exposure levels to specific respirable animal allergens. Second, what is the natural history of the development of allergy and asthma to lab animals? How do changes in factors such as exposure to animals, airway hyperreactivity, specific IgE and IgG, skin test reactivity, and symptoms relate to one another and to other factors, in a temporal sense in the development of disease? These questions are being addressed in a longitudinal study of 500 research lab workers with minimal prior exposure to the animals and who do not have asthma to the animals at the time of entering this longitudinal study. Subjects are evaluated at 6-month intervals for at least 30 months, with the following: personal interviews; tests for immunologic reactivity (skin tests, serum IgE and IgG antibodies); and tests of airway reactivity (bronchoprovocation with mechalyl). The degree of exposure to animal allergens is quantitated by aeroallergen sampling of workplace and personal breathing zone air, and by Work Diaries. Laboratory animal allergy provides an excellent model of occupational asthma, and increasingly important problem. An improved understanding of mechanisms and risk factors will contribute to successful prevention not only of asthma and allergy to lab animals but also of allergic disorders not limited to the occupational environment.